This invention relates to a door structure for a microwave oven and more particularly to an improved door structure for a light-weight microwave oven which is becoming popular recently.
As shown in FIG. 3, a microwave oven door of a previously developed type is comprised of a door panel 31 which closes the cooking chamber (not shown) formed in the housing (not shown), a box-shaped door screen 32 of synthetic resin covering the external surface (distal the cooking chamber) of the door panel 31 and a transparent film 33 pasted onto the internal surface (on the side of the cooking chamber) of the door panel 31. Many small holes 34 are formed in the door panel 31 such that the interior of the cooking chamber is visible from outside. These holes 34 are covered by the film 33 in an airtight manner such that the vapor generated inside the cooking chamber is prevented from invading the space between the door panel 31 and the door screen 32 and that objects like a piece of wire are prevented from entering from outside into the cooking chamber.
Another previously developed microwave oven door is shown in FIG. 4A which is a sectional view of a part thereof and FIG. 4B which is its perspective view, and comprises a door panel 41 and two transparent films 42 and 43 structured identically and pasted to both air-tightly surfaces of the door panel 41. As in the previous example shown in FIG. 3, this door panel 41 is also provided with a large number of small holes 44 created by a continuous punching method which is convenient for the purpose of mass production. Numerals 45 and 46 indicate layers of an adhesive material.
The door structure as shown in FIG. 3 is relatively heavy and expensive because a molded synthetic resin product is used. The door of FIG. 4 has the advantage of being light but since the films 42 and 43 are attached to the door panel 41 such that the small holes 44 made in the door panel 41 are completely blocked, air trapped in the holes 44 by the two films 42 and 43 expands as its temperature rises by the heat from the cooking chamber. This frequently causes the films 42 and 43 to become separated from the door panel 41 and to develop wrinkles on their smooth surfaces. The external appearance of the door is thereby adversely affected and the user will feel uneasy or unsafe to use such an oven.